Conventionally, there is known a wafer holding apparatus for performing alignment of the center position and direction of a wafer placed by a wafer transfer robot (for example, see patent document 1). Such a conventional holding as disclosed in this patent document is provided with a plurality of slide arms (holding mechanisms) opened or closed in the wafer center direction, each of the slide arms having a claw at an outer edge for holding an outer circumference of the wafer.    [Patent Document 1] Japanese Patent Application Laid-open No. 2006-222190